How to even get the sword? (i'm just really don't know)
As soon as you leave the Queen's cell, avoid enemies and go through the rooms on the right. The first room has a waterfall, the room after that will have a big pit in the ground.
The pit room will have a glowing sword next to a skeleton, all you need to do is interact with the sword and you'll get weapons for everyone. Don't forget to manually equip ghe weapons afterward!